Lots of problems here... I'm an experienced Mastodon user, and I have to say that I correctly predicted my experience with Lemmy.
It's not optimized for mobile, it's a lot of work to find what you want, and whereas Mastodon seems like an improvement on Twitter, this seems like a step back from Reddit.
Reddit also has an issue with finding subreddits, but Google indexes it and you can pretty easily find and subscribe to things just using keywords.
We need better app UIs ASAP, that make basic functions obvious and easy. It's a platform that probably does great on PC but I'm stuck with Jerboa, and it's really killing my enjoyment.